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From the following data, $$\begin{array}{c}\mathrm{C}(\text { graphite })+\mathrm{O}_{2}(g) \longrightarrow \mathrm{CO}_{2}(g) \\\quad \quad\quad\quad\Delta H_{\mathrm{rxn}}^{\circ}=-393.5 \mathrm{kJ} / \mathrm{mol} \\\mathrm{H}_{2}(g)+\frac{1}{2} \mathrm{O}_{2}(g) \longrightarrow \mathrm{H}_{2} \mathrm{O}(l) \\\quad\quad\quad\quad\Delta H_{\mathrm{rxn}}^{\circ}=-285.8 \mathrm{kJ} / \mathrm{mol} \\2 \mathrm{C}_{2} \mathrm{H}_{6}(g)+7 \mathrm{O}_{2}(g) \longrightarrow 4 \mathrm{CO}_{2}(g)+6 \mathrm{H}_{2} \mathrm{O}(l)\\\quad\quad\quad\quad\Delta H_{\mathrm{rxn}}^{\circ}=-3119.6 \mathrm{kJ} / \mathrm{mol}\end{array}$$calculate the enthalpy change for the reaction $$2 \mathrm{C}(\text { graphite })+3 \mathrm{H}_{2}(g) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{6}(g).$$

$-84.6 k J / m o l$

Chemistry 101

Chapter 6

Thermochemistry

University of Maryland - University College

University of Kentucky

University of Toronto

Lectures

05:27

In chemistry, a chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Both reactants and products are involved in the chemical reactions.

06:42

In chemistry, energy is what is required to bring about a chemical reaction. The total energy of a system is the sum of the potential energy of its constituent particles and the kinetic energy of these particles. Chemical energy, also called bond energy, is the potential energy stored in the chemical bonds of a substance. Chemical energy is released when a bond is broken during chemical reactions.

Given the following data

04:10

From the following heats o…

07:26

So for this question, were given three chemical equations and given their del teaches, and we're trying to find the Delta h of a specified chemical reaction. So for this first equation, you know that the Delta H is negative. 393.5 Killer jewels Permal The second equation Yes, Mattel to each this negative 285 0.8 killer jewels for more in the final reaction is this. And then the Delta H is negative. 3000 119.6. Killer jewels Prum Old on the desired reaction of a desired equation, it's two moles of carbon graphite, three moles of hydrogen gas and then, on the right side, one more of C two h six. So when you're solving these types of problems, it's very important to write down each equation so you can clearly see the relationships in terms of the more ratios and what's on the left side versus what on the right side. So let's look at the desired equation and go step by step. The first thing we want is you want to moles of carbon graphite on the left side, and then you look at the 1st 3 equations. The only equation that has any moles of carbon graphite is the 1st 1 right here. It's on the left side, just as we wanted to. But in consider being two moles like we want in the desired equation to do only one mole. So we're gonna multiply this entire equation, including the Delta H by two. And that will give us to two moles of carbon graphite that we want in the left side. Now the next thing that we want is three moles of hydrogen gas. Now, once again, the only equation that contains any moles of hydrogen gas is the 2nd 1 And instead of being three most, it's only one more. But because it's also on the left side, which is a crack side, the only thing that we need to do is want to buy this entire equation by three. And I don't give us that three moles of hydrogen gas. Everyone, the last thing that we want to do is we want to get C two h six I. Only the third equation contains C two h six, but there's two problems here. The first is that it's on the left side of the equation instead of the right side, so we need to fix it. But more importantly, there's two moles of C two h six in the third reaction. While we only want one more so to correct for both, these things go to multiply this by negative 1/2 where the negative flips aside and the 1/2 decreases it, only one more. So then the last thing that we need to do is we simply need to take into account for all of the Delta. H is that we multiplied to get the final Delta H for the desired reaction so we can express this as the following two times negative 309 3.5 plus three times a lady 285 point and then minus 1/2 of negative 3100 in 19.6. And then finally, when you put all of that into your calculator, you will get But the dealt age for the desired reaction Here is negative 84.6 killer jewels per mole, and that is the final answer

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